Tony Stewart, driver of the #14 Code 3 Assoc/Mobil 1 Chevrolet, is inducted into the Sonoma Raceway Wall Of Fame after practice for the NASCAR Sprint Cup Series Toyota/Save Mart 350 at Sonoma Raceway on June 24, 2016 in Sonoma, Calif.

SONOMA, Calif. — There was a twinge of nostalgia in Tony Stewart’s voice as he was inducted into the Sonoma Raceway Wall of Fame.

Then his mood quickly turned as he talked about the reasons he’s retiring from NASCAR competition at the end of the season.

“I’m ready to go run stuff that makes me happy, and driving a Sprint Cup car does not make me happy right now,” the 45-year-old Stewart said Friday. “A lot of things have changed. The atmosphere has changed. There’s so much stuff in the garage area that’s changed that it was time for me to make a change with it.

“I’ve dedicated 18 years of my life to this series and it’s done great by me — I’ve made a great living doing it. But at the same time, there are other things in life I want to do other than be at a NASCAR track three days a week for 38 weekends out of 52 weeks a year.”

Stewart is a two-time winner at Sonoma, and Sunday’s race will be his final one on the road course. Then comes Daytona next week, for his final appearance as a driver at that vaunted track.

But when he starts to feel sad about the close of a career, he’s reminded that there is more to life than just NASCAR. He said the 38-week schedule encompasses a driver’s entire life, and retired friends Don Prudhomme and Ray Evernham had made life away from the race track sound pretty appealing.

“I can’t imagine there’s not more to life than this,” he said. “I know there is. I know people that talk about it all the time.”

Part of Stewart’s comments Friday reflected his frustration with practice, which ended in an incident with Jamie McMurray. Stewart flipped his middle finger at McMurray because he thought McMurray had ruined his lap.

“Some of the things these guys do nowadays doesn’t make sense,” Stewart said. “When we had Dale (Earnhardt) Sr. and Rusty Wallace and Dale Jarrett, they were able to get their arms around these guys and get them to listen and make sense. There’s really nobody here that can do that anymore. Everybody is out of control.”

But Stewart wouldn’t bite when asked how to change the attitudes of the younger drivers.

“I’m not even going to talk about those guys,” he said. “It’s not worth it.”

Lowe's, one of the last remaining corporate giants in NASCAR, announced Wednesday that it will not sponsor seven-time champion Jimmie Johnson after this season, an ominous sign for the nation's top racing series.